Effect of lanthanide contraction on the Ln/Sb/Se/dien system: solvothermal syntheses and characterizations of lanthanide(III)-selenidoantimonate complexes with diethylenetriamine as a co-ligand

Abstract

The ternary system Ln/Sb/Se was investigated in a diethylenetriamine (dien) solvent under solvothermal conditions and two types of neutral lanthanide(III)–selenidoantimonate complexes [Ln(dien)2(μ-η1,η2-SbSe4)]n (Ln = Pr(1), Nd(2)) and [Ln(dien)2(η2-SbSe4)] (Ln = Sm(3), Gd(4)) were prepared. The lanthanide ions form [Ln(dien)2]3+ cations with two dien chelating ligands. In 1 and 2, is a tridentate μ-η1,η2-SbSe4 bridging ligand to connect [Ln(dien)2]3+ into one-dimensional coordination polymers [Ln(dien)2(μ-η1,η2-SbSe4)]n; it coordinates to [Sm(dien)2]3+ and [Gd(dien)2]3+ as a η2-SbSe4 bidentate chelating ligand, forming 3 and 4. Ln3+ in 1–2 and 3–4 are nine- and eight-coordinate environments, forming distorted monocapped square antiprisms and bicapped trigonal prisms, respectively. The different coordination modes of between 1–2 and 3–4 are related to size of Ln3+. Complexes 1–4 exhibit semiconducting properties with band gaps of 2.08–2.28 eV.